TEHRAN, Iran (AP) — Iran’s foreign minister said Sunday his country will continue nuclear negotiations with world powers, even after pulling out of expert-level talks to protest the U.S. targeting companies it says evaded current sanctions.

Writing on Facebook, Foreign Minister Mohammad Javad Zarif blamed “improper actions” by the U.S. for Iran pulling out Friday. Technical experts from six world powers and Iran — which negotiated a deal in November to freeze Iran’s nuclear activity for six months in return for no new sanctions — had been meeting in Geneva to discuss implementing the arrangement.

“We will continue Geneva talks. We will show proper, calculated, purposeful and smart reaction toward any improper and unconstructive action,” Zarif wrote on Facebook, which average Iranians can’t normally access. “Over the past days, improper actions were carried out by Americans that we responded in a proper way.”

He also wrote: “Talks and reaching a conclusion is a difficult job and it will definitely have ups and downs. ... We had predicted this from the first day.”

Thursday’s action by the U.S. freezes the American assets of firms in Panama, Singapore, Ukraine and elsewhere for maintaining covert business with Iran’s national tanker company. Other companies involved directly in the proliferation of material useful for weapons of mass destruction also were blacklisted from the U.S. market. American citizens are banned from any transactions with the listed individuals and firms.

The U.S. move comes as Republicans and Democrats in Congress have called for even tougher measures to raise the pressure further on the Islamic Republic, despite the administration’s pleas for patience.

The West fears Iran’s nuclear program could allow it to build nuclear weapons. Iran says its program is for peaceful purposes like power generation and medical treatment.

Zarif and the government of moderate President Hassan Rouhani also face criticism at home by hard-liners over the Geneva deal — and Thursday’s sanctions. The foreign minister also addressed them in his Facebook post.

“Some friends who were not happy with the Geneva action plan have announced its early death, which is an expression of their wish rather than the reality,” Zarif wrote. “We will answer all the criticism and ambiguities in appropriate time.”